VECTREX

Well Neil... I hope this is okay for the list since it is not about an arcade
game, but the only home vector system... the VECTREX.
Anyway, here we go.

I just got a Vectrex system from a fiend of mine. Normally I work with Atari
Vector games like Tempest or Starwars, and he knew I was into Vector games :)

Anyway, it was broken to start with. Some probing showed the 6522 was shot and I
replaced it. Now everything works fine, except for one strange thing: Every
second letter of any text shown in minestorm (don't know what happens when I use
a cart since I do not have one yet) is blank! nothing!

The only cause I can think of is a stuck lower address line, but since there is
only one ROM which stores more than just plain text, this can't be really true.
My logic analyzer shows it is indeed still alive. When I check the content of
the ROM by looking at an image from an emulator for the Vectrex, you can see
the display texts are scattered around the ROM . This leads me to the idea it
really cannot be an adressing problem. Also high scores are crippled and they do
not come from ROM but RAM, is it?

Does anyone have a clue were to look next?

Another thing I don't understand how the Vectrex 'draws' the vector. In the
normal vector stuff, as you all know, there is a separate 'vector generator'
with it's own instruction set, RAM and ROM, vector counters ect ect. The game
processor only has to send a bunch of co-ords and the vector generator will do
it for it. (basically).

In the Vectrex, there is only the 6522 I/O controller using the same bus for
sending audio and DAC data. Does this mean the 6809 is actually generating all
vectors by throwing X, Y, Z and 0 ref digital data to the 0808DAC all by itself?
Could someone clarify this for me, as I really want to know how this is done!

Kind regards,

Mendel
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Received on Wed Sep 13 19:14:16 2000